In recent years, the widespread use of devices having cathode ray tube (CRTs) has created certain problems. For instance, computer terminals, televisions, and video games are known to have increased the amount of stray energy emitted into the environment in the vicinity of such devices. The art commonly refers to such energy as electromagnetic energy interference (EMI) or radio frequency interference (RFI). There is a need, not only to protect people who may be particularly affected adversely by such interference (such as people having heart pacemakers) but also to protect sensitive electronic equipment from damage caused by such interference. Moreover, it is known that such energy can be intercepted and information obtained therefrom by sensitive electronic surveillance equipment.
While it is not difficult to shield CRT cabinets from both emission of, and penetration by, such forms of energy, it is difficult to provide satisfactory shields, or filters, for the screens of cathode ray tubes, and other information transmitting devices, such as light emitting diodes (LEDs). This is because of the need for operators to be able to read information from the devices with a minimum of optical distortion caused by the filter.
U.S. Pat. Nos. 3,305,623; 3,431,348; and 4,247,737 disclose viewing panels for use with cathode ray tubes to attenuate the transmission of energy across the front of the cathode ray tube screen. Each of these patented filters is characterized by a loosely knit mesh wire material laminated between transparent glass or plastic panels. Most of the filters of this type are flat, although curved laminated filters are commercially available.
Viewing panels particularly suited for use with microwave ovens are disclosed in U.S. Pat. Nos. 4,008,383; 4,010,343; and 4,264,800.
Various shielding devices for use in attenuating electromagnetic energy are disclosed in the following U.S. patents: U.S. Pat. Nos. 2,674,644; 2,875,435; 3,030,435; 3,126,440; 3,265,804; and 4,037,009.
Various filters have been proposed for attenuating reflections of ambient light. For example, in U.S. Pat. No. 2,977,412 and U.S. Pat. No. 4,253,737, there are disclosed mesh type screens for use in combination with cathode ray tubes for this purpose. The former patent suggests the use of either metallic or synthetic fiber filaments. Neither patent, however, is concerned with the attenuating EMI or RFI energy.
U.S. Pat. No. 4,163,821 discloses an adhesive bonding procedure for providing mechanical stabilization of metallic glass ribbons in fabric form.
While each of the above noted patented inventions may function satisfactorily for its intended purpose, there is a demand for an improved cathode ray tube filter which provides energy attenuation capabilities, which is free from optical defects, and which is capable of being manufactured efficiently.